Railroad hopper cars are commonly used to economically transport commodities between distantly spaced geographic locations. Dry granular commodities can be rapidly discharged from the hopper car through gate assemblies mounted in material receiving relation relative to standard openings on a bottom of the hopper car. Each gate assembly typically includes a frame defining a discharge opening. A gate is slidably movable on the frame and a drive mechanism is provided for moving the gate between closed and open positions. In a closed position, the gate is typically supported on ledges or runners extending inwardly of the discharge opening from opposed sides of the gate assembly frame. When closed, the gate prevents discharge of the commodity from the hopper car. When the gate is opened, the commodity is gravitationally discharged through the discharge opening defined by the gate assembly.
The hopper car usually includes a mounting flange provided about each standard opening on the bottom of the hopper car. Such hopper car mounting flange typically defines a series of apertures or openings arranged in a generally standard bolting pattern. The gate assembly frame includes, toward an upper end thereof, a mounting flange designed to facilitate securement of the gate assembly to the hopper car. A transition wall section angles inwardly from the mounting flange on the gate assembly frame toward the discharge opening for the gate assembly. That is, the angled or slanting transition wall section converges toward the discharge opening and helps to reduce net columnar loading on the gate from the commodity in the railcar. As will be appreciated, and while helping to reduce net columnar loading on the gate, the converging walls in the transition section of the frame also narrow or reduce the cross-sectional area or size of the discharge opening. A standard discharge opening on a gate assembly measures approximately 30 inches by 30 inches or approximately 13 inches by 42 inches.
Because of serious concerns over costs, corn is a one type of commodity typically transported in railroad hopper cars. Currently, in an average year, millions of bushels of shelled field corn are transported in hopper cars from individual farms to industrial corn processing plants. This percentage of “industrial use” versus the amount of corn produced has steadily increased over the decades from 9.9% in 1980 to 17.9% in 1990 to the current 19.7%.
The industrial processing of corn for ethanol production provides an important value-added market for farmers. In America, record corn crops combined with declining export markets has resulted in the lowest corn prices in twenty years. As the third largest use of corn behind only feed and exports, ethanol represents a market for over 600 million bushels of corn a year. Today, there are 62 production facilities located across the United States manufacturing renewable fuel ethanol. Since 1980, the production of ethanol fuel has increased over 800%.
Using a process called wet milling, a kernel of yellow dent corn is separated into products which, in turn, are further processed into many other products, one of which is ethanol fuel that utilizes only the starch, an abundant and low-value component. A variety of other valuable feed co-products are also obtainable from the corn. For example, corn gluten feed is a by-product of the wet milling process. Wet corn gluten feed represents an excellent feedstuff having broad applications in both the beef and dairy cattle industries. Corn gluten feed contains significant amounts of energy, crude protein, digestible fiber, and minerals.
Wet corn gluten feed has several advantages over dry corn gluten feed. For example, wet corn gluten feed is more digestible than dry corn gluten feed and can replace up to 50% of dry rolled corn or 30% steam-flaked corn in beef finishing diets without negatively affecting performance. As such, wet distillers grains help livestock producers lower feed costs by using locally produced high-quality feeds. Moreover, production of wet corn gluten feed allows the plants to eliminate the expense of drying the material, which is quite costly. Of course, such cost savings can be realized by the producer.
There are some serious disadvantages, however, associated with wet corn gluten feed. For example, when stored in an open pile for a few days in warm weather mold growth develops and spoilage is rapid. Shipping wet corn gluten feed in a hopper or walled enclosure of a railcar advantageously reduces spoilage while facilitating economic transportation of the feed material from the processing plant to the end user within minimum time periods.
Additionally, wet corn gluten feed requires special unloading procedures. Typically, wet corn gluten feed has a sticky texture resembling oatmeal. The wetness of the corn gluten product significantly increases the columnar load acting on the gate assembly and, particularly, the gate of the gate assembly. Moreover, the stickiness of the wet feed significantly reduces its flow characteristics, thus, making handling and unloading of the wet feed difficult. Settling of the commodity during transit can cause significant additional problems during unloading of the wet corn gluten feed from the railcar.
Once a hopper car reaches an unloading site, the gate assembly is opened and gravity normally causes the commodity within the walled enclosure or hopper on the car to readily flow therefrom. The reduced flow characteristics, however, of wet corn gluten feed, especially when combined with the tendency of such material to settle during transport, has caused bridging of the corn gluten material across the discharge opening, thus, creating problems in unloading the railcar. The gate supporting ledges extending inwardly toward the discharge opening on the gate assembly tend to promote the formation of a bridge or material plug extending across the discharge opening while furthermore inhibiting mass flow of material, thus, exacerbating the problem of moving sticky materials through the discharge opening of the gate assembly.
One proposed solution to such problems involves inserting a powered driver down through the hopper car roof and into the walled enclosure to forcibly push the wet corn gluten feed through the gate assembly. Besides adding significant costs to the unloading procedure, as they plunge through the hopper, such drivers often cause damage to the interior of the walled enclosure or hopper on the railcar. Such drivers have also been known to further compact the material, thus, creating a plug or bridge at the lower portion of the material to set like concrete. Alternatively, the sides of the walled enclosure are manually struck with large hammers in an effort to try to loosen the wet feed material and create advantageous flow thereof. The converging walls forming the transition section on a typical gate assembly design exacerbates the problem of having the wet corn gluten feed move through the reduced opening in the gate assembly. Moreover, known gate assemblies are neither designed nor structured to operate under the net increased columnar loads imparted thereto by the wet corn gluten product.
To further complicate the gate assembly design, the Association of American Railroads (the “AAR”), revised the Standard governing locking systems for gate assemblies used on hopper-type railroad cars. The revised Standard (S-233-92) requires the locking/unlocking or latching/unlatching functions for the gate assembly to be integrated into the discharge gate operating mechanism. As such, rotation of a capstan in a direction to open the gate must first unlock or unlatch the gate and then move the gate from the closed position to the open position.
Thus, there is a need and continuing desire for a railcar gate assembly which can withstand the net increased columnar loading placed thereon by wet feed products transported within a walled enclosure of a hopper car while allowing for gravitational discharge of both granular product as well as wet, sticky material or commodity therethrough with minimal intervention while satisfying the latest AAR Standard.